Almond leaves, also called Indian almond leaves (IAL), are used in home aquariums as a water conditioner. Their benefit remains unproven scientifically, but many fish keepers claim they are good from their fish. Almond leaves are said to be beneficial for the betta, also known as the Siamese fighting fish, by adding substances called tannins to the water. Anecdotal evidence suggests that these tannins improve the habitat by making it more brackish, which is to a betta’s liking and mimics its Southeast Asian home waters. Almond leaves also are said to speed healing, encourage better health overall and promote optimum spawning conditions.

The tannins from almond leaves will change the acidic level in the tank, lowering it to a range that bettas prefer and thrive in. This natural substance can block fungus growth and strengthen a betta’s immune system. Tannins can also be introduced into an aquarium by driftwood, and many aquarists who prefer not to change the level of acidity in their tanks will soak the driftwood before placing it in their tanks to remove much of the tannins.

In Asia, bettas are prepped for their fighting displays by exposure to almond leaves. It is believed this exposure prevents serious injury by hardening and smoothing the fish’s scales, preventing another betta from biting hard enough to inflict more serious wounds. The fish are pre-treated with almond leaves for a week, and then treated again after the fight to promote healing after the battle.

Almond leaves are also commonly known as ketapang leaves and catappa leaves. Other types of fish that have been shown to benefit from their inclusion in the fish tank are catfish, rasbora, tetras, discus and dwarf cichlids. Additional benefits include the promotion of more vibrant colors in the fish and healthier fins, plus the discouragement of parasites.